Ca12Al14O33 or MgO supported Ni-carbide slag bi-functional materials for H2 production and CO2 capture in sorption-enhanced steam gasification of cellulose/polyethylene mixture

Abstract

Co-gasification of biomass and waste plastics is a promising technology for H2 production. In this work, Ni-CaO-Ca12Al14O33 and Ni-CaO-MgO bi-functional materials were prepared from carbide slag for H2 production in sorption-enhanced steam gasification experiments of cellulose/polyethylene mixtures. The H2 production and CO2 capture performances of Ni-CaO-Ca12Al14O33 and Ni-CaO-MgO in sorption-enhanced steam gasification of cellulose/polyethylene were studied and compared. Density functional theory calculations, including the density of states, electron differential densities, and adsorption energies were performed to investigate the effect of supports on the stability and reactivity of Ni-CaO-based bifunctional materials at a microscopic level. The results exhibit that polyethene contributes to improving the H2 production effectiveness of cellulose sorption-enhanced steam gasification, the optimum mass ratio of cellulose to polyethene is 0.5:0.5. The CO2 capture capacity, H2 yield, and H2 concentration using Ni-CaO-Ca12Al14O33 can be respectively 2.0, 2.6, and 1.4 times as high as those using Ni-CaO-MgO in the 20th cycle, which indicates the higher cyclic stability and catalytic activity of Ni-CaO-Ca12Al14O33. Density functional theory results also indicate that Ca12Al14O33 can better retain the stable structure of Ni-CaO-based materials, which is consistent with the experimental results. Compared with MgO, Ca12Al14O33 is a better framework for Ni-CaO-based bifunctional material for H2 production in the sorption-enhanced steam gasification process.